Abstract: AIM: To compare the laryngeal mask insertion conditions at different plasma target concentrations (Cp) during the induction of anesthesia with target-controlled infusion (TCI) of propofol combined with dexmedetomidine. METHODS: Seventy-five ASA I-II patients of both sexes aged 20-60 years, weighing 50-80 kg, in which the use of laryngeal mask was indicated were randomly divided into 3 groups (n=25) according to Cp of propofol set during induction of anesthesia: 2.0, 2.5 and 3.0 μg/mL.Dexmedetomidine 0.6 μg/kg was infused over 10 minitues. Then,TCI propofol was given by Diprifusor (Graseby 3500 infusion pump).Laryngeal mask was inserted when the effect-site concentration (Ce) of propofol reached the settled Cp. Laryngeal mask insertion conditions (jaw mobility,coughing,head and limb movement,laryngeal spasm) were assessed. SBP, MAP, HR and BIS value were recorded at four time points:baseline before induction (T₀), instant before laryngeal mask inserted (T₁), 1 min (T₂) and 3 min (T₃) after insertion of laryngeal mask. Changes of SBP, MAP and HR between T₁ and T₀ were calculated. The number of patients with apnea and apnea times were recorded. The administration of atropine and ephedrine was also recorded. RESULTS: The levels of SBP, MAP and HR were decreased with increasing depth of anesthesia in the 3 groups.The decline rates of SBP, MAP and HR after induction had significantly differences in group III than those in group I and II (P<0.05). BIS value was similar in all groups. The insertion conditions were significantly better in group II and III than that in group I. More patients developed apnoea and their apnoea times were longer in group III than the other two groups (P<0.05). More patients were administrated with atropine and ephedrine in group III compared with the other two groups (P<0.05).CONCLUSION: Induction of anesthesia with dexmedetomidine 0.6 μg/kg combined with TCI of propofol with Cp set at 2.5 μg/mL is satisfactory for laryngeal mask insertion in terms of cardiovascular stability and insertion conditions.

Key words: Propofol, Dexmedetomidine, Target-controlled infusion, Laryngeal masks